Last.fm has lost tracks from Warner Music Group (NYSE: WMG) artists after the label let its contract with the music site expire, complaining returns from the deal have “come up short”. Despite becoming the first major to offer its repertoire to the site last year, WMG is disappointed Last.fm still hasn’t launched its much-promised subscription fee programme, according to executives quoted by NYT.

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And payback the label gets from the existing service has not met expectations, they say, explaining that per-play fees had been too little because usage had been lower than expected. WMG is also said to want a greater slice of revenue from ads shown next to music players (it currently gets per-track royalties plus a rev share from some ads).

Though WMG tracks are still included in Last.fm’s non-interactive radio streaming feature, it’s a blow to the site, which had built its major-label credentials on that initial Warner deal. Last.fm said back in January it would add a new premium subscription structure, allowing users to play tracks an unlimited number of times for a monthly fee. Last.fm says the unlimited service has increased Amazon sales by 119 percent but that subscription still hasn’t launched and Last.fm is now both building a new-look site and working on cross-promotion opportunities with CBS.

It only issued a statement saying: “We are currently negotiating a new agreement with Warner Music Group…” Wired wonders if WMG is pushing for an equity stake.